1. Field of the Invention
The present invention relates to a drive unit including a vibration actuator using a piezoelectric element.
2. Description of Related Art
A drive unit including a vibration actuator using a piezoelectric element is known (cf., Japanese Unexamined Patent Publication No. 2004-304963) and used in ultrasonic motors and devices which make small step-by-step displacement.
The vibration actuator is placed between a stationary body and a movable body arranged movably relative to the stationary body. Specifically, the vibration actuator is fixed to one of the stationary and movable bodies with part thereof (e.g., a driver element) outputting a driving force in touch with the other one of the stationary and movable bodies (hereinafter may be referred to as a touched body). When the drive unit applies an electric field to the piezoelectric element of the vibration actuator in this state, the piezoelectric element is displaced due to its piezoelectric characteristic and the vibration actuator makes vibration (e.g., longitudinal vibration and bending vibration). As a result, the movable body is moved in a predetermined direction by friction caused between the vibration actuator and the touched body.